M. Abreu

Gamma spectroscopy and optoelectronic imaging with hybrid photon detector

Abstract Hybrid Photon Detectors (HPD) detect light via photocathodes and accelerate the emitted photoelectrons by an electric field towards silicon PIN-anodes, where they are absorbed and generate electronic signals. We have developed two specific types of HPDs: (1) Hybrid photomultiplier tubes for photon counting and gamma spectroscopy; (2) Imaging silicon pixel array tubes for optoelectronic cameras. This paper will illustrate the main achievements, which we obtained in the last years, and will describe and discuss our present main RD 29.40; 29.30; 87.59

A new ultra radiation hard cryogenic silicon tracker for heavy ion beams

AbstractWe have designed and built a new hodoscope for heavy ion beams consisting of two tracking stations equippedwith silicon microstrip detectors operated at 130K. Preliminary results from tests performed in the high intensityCERN-SPSPbionbeamshowthatwewereabletodetectandidentifyeachincomingionuptoabeamintensityofB10 7 ions/s.Thebeamprofilecouldbemonitoredon-linewith50mmresolution.Thedetectorperformedsatisfactoryevenafteradoseof90740Grad.r 2002ElsevierScienceB.V.Allrightsreserved. PACS:07.77. n;85.30.ZKeywords:Cryogenicsilicondetectors;Heavyions 1. IntroductionIn the framework of the CERN NA60 [1] andRD39Collaborations [2], we have developed anew cryogenic beam hodoscope, hereafter namedBeamscope, based on silicon microstrip detectorsoperated at 130K. This detector represents thefirst application in a high energy physics experi-mentofthecryogenicsilicontechnology,triggeredbythediscoveryofthe‘‘Lazaruseffect’’[3]in1998anddevelopedbyRD39.Operationofsiliconatcryogenictemperaturesisanattractivetechnologyindeedforapplicationinharsh environments. It has been shown [4,5] thatheavily irradiated silicon detectors operatedaround 130K have charge collection efficiency

Raising the bar (1)

Abstract In this editorial, we summarize and comment on the papers published in issue 11.1 so as to raise the bar in applied spatial economic research and highlight new trends. The first paper employs the J-test to discriminate between two economic-theoretical explanations for the wage curve. The second applies a two-step ML procedure to measure the impact of volatility on economic growth. The third tests for endogeneity in the Spatial lag of X (SLX) model and whether or not the model should be extended to contain a spatial lag. The fourth utilizes the gravity model to test whether or not grids should be merged into larger units of observations. Finally, the last adopts a time-space recursive model to test the ripple effect and (linguistic) border effect hypotheses on housing prices in Belgium.

First experimental results with the Clear-PEM detector

First experimental results of the imaging system Clear-PEM for positron emission mammography, under development within the framework of the Crystal Clear Collaboration at CERN, are presented. The quality control procedures of crystal pixels, APD arrays and assembled detector modules are described. The detector module performance was characterized in detail. Results on measurements of light yield, energy resolution, depth-of-interaction and inter-channel cross-talk are discussed. The status of the development of the front-end electronics and of the data acquisition boards is reported.

Raising the bar (4)

Abstract This editorial summarizes and comments on the papers published in issue 11(4) so as to raise the bar in applied spatial economic research and highlight new trends. The first paper deals with common factors and spatial dependence in the error term specification of a production function model. The second paper sets forth a New Economic Geography (NEG) model with production activities that vary in their complexity, so as to analyse the impact on specialization patterns across different regions. The third paper measures the efficiency of local public investments using a relatively unknown econometric technique in which the time span over which the variables in the regression equation are measured is increased by one time period every run. The fourth paper adopts a conditional quantile regression approach to determine the impact of people employed in informal jobs on the wage distribution in Colombia and five of its regions. Finally, the last paper proposes and tests two new Bayesian variable selection approaches for spatial econometric models.

Silicon detectors irradiated ''in situ'' at cryogenic temperatures

Though several studies have proved the radiation tolerance of silicon detectors at cryogenic temperatures, following room temperature irradiation, no previous investigation has studied the behaviour of detectors irradiated ‘‘in situ’’ at low temperatures. In this work, effects of irradiation of 450 GeV protons at 83 K will be presented, showing that after a dose of 1.2 � 10 15 pc m � 2 a charge collection efficiency (CCE) of 55% is reached at 200 V before the annealing. The same results were found at the end of the irradiation, after the sample has spent more then one year at room temperature. This shows that the CCE recovery by low temperature operation is not affected by the temperature of irradiation and by the reverse annealing. r 2002 Elsevier Science B.V. All rights reserved.

Raising the Bar (3)

Abstract This editorial summarizes and comments on the papers published in issue 11(3) so as to raise the bar in applied spatial economic research and highlight new trends. The first paper proposes spatial and a-spatial indicators to describe the networks of airline companies around the world. The second paper sets forth a two-regime gravity-type model with an endogenous threshold parameter to assess the effect of labour market conditions on interregional migration flows. The third paper utilizes micro-data to explain student migration flows to higher education institutions. The fourth paper is among the first to make use of simulation-based location quotients in a multiregional input–output model. Finally, the last paper provides a purely economic–theoretical model on cooperative limit pricing in the context of spatial competition.

Further readout electronics development for the ISPA gamma camera

The ISPA (Imaging Silicon Pixel Array)-tube is a position sensitive photon detector based on the hybrid technology. It detects light via a photocathode and an appropriate electric field accelerates the emitted photoelectrons towards a silicon pixel anode. This anode, finely segmented into pixel detectors provides binary images and allows for the self-triggering of the tube. Coupled to scintillating crystals, ISPA-tubes have been successfully tested in the field of gamma ray imaging, demonstrating real capabilities in both space and energy resolution. Recently, we have concentrated our efforts on the development of a compact and portable readout system based on new electronics and able to provide full control and real-time processing of ISPA-tubes. The system overview and the dedicated interface are presented in this paper.

Recent progress in low-temperature silicon detectors

The CERN RD39 Collaboration studies the possibility to extend the detector lifetime in a hostile radiation environment by operating them at low temperatures. The outstanding illustration is the Lazarus effect, which showed a broad operational temperature range around 130 K for neutron irradiated silicon detectors.

Cryogenic technology for tracking detectors

A low-mass cryogenic cooling technique for silicon sensor modules has been developed in the framework of the RD39 Collaboration at CERN. A prototype low-mass beam tracker cryostat has been designed, constructed and tested for applications in fixed target experiments. We shall report here briefly the main features and results of the system.